Splattered blood on the rocks of Prospect Park, smashed turtle shells, a suspicious attempt at a campfire — and finally, arson in the reedy underbush.

It’s not the latest Linda Fairstein mystery novel — it’s a chronology from last week along the lakeshore in Brooklyn’s green heart.

Park-goer Susan Yuen noticed the first of the disturbing events — the blood-spattered rocks on the shoreline of the lake near Prospect Park Southwest.

There was blood, lots of it, pooled on the rocks and seeping into the sullied soil. This wasn’t a mere paper cut or skinned knee. This was murder.

Someone had clearly used the rock as a rudimentary chopping block.

“It was still wet,” said Yuen, shaken from the last Sunday discovery. “At first I thought the blood was from the swans.”

Fortunately, Honeybear and the rest of the celebrity waterfowl were in good health, but were keeping away from their regular haunts — a sign to the bird-lovers that something traumatic had happened.

Yuen headed for the nearby Audubon Center in the boathouse and notified the naturalists, who analyzed the crime scene photos.

“If it is blood, probably not from a bird, even if was sitting in one spot, slowly bleeding over a long period of time,” the naturalists concluded. “It seems that would have to be a pretty big fish for that big a pool blood. And for it to collect that densely on the top of the dirt and the rock, like a pour, it’s probably not likely.”

The message went on to say that a dog attack seemed unlikely, as out-of-control dogs generally “go for a kill … and then try to break the neck. But they don’t sit there and rip it apart.”

If it had only been some blood on the rocks, that would have been alarming enough, but that macabre incident was only the beginning.

By Thursday morning, more blood had appeared at the crime scene, meaning that someone — or something — sadistic had repeated the grisly deed.

Unofficial park watchdogs Ed Bahlman and Anne-Katrin Titze, who have become leading advocates for swan safety, were quickly alerted, and their keen eyes noticed other disturbing clues.

A few feathers were scattered about a splotch of blood on a tree by the lake — was some desperate or demonic soul capturing the waterfowl for a meal?

“But where are the bones? There is no carcass,” Titze said. “It goes against any theory that an animal could have caught it. It’s too clean and butcher-y.”

To add to the mystery, there was an arrangement of sticks in a campfire-like pile nearby.

While contemplating the significance of these unsettling signs of malfeasance, Titze and Bahlman came upon another disturbing site: someone had smashed turtle shells in the middle of the path opposite the boat house. They were picked clean of flesh.

“Sure, an animal could have eaten [the meat],” said Bahlman. “But someone would have had to smash them.”

He ominously added, “Somebody is doing something mean-spirited.”

But that very night, this unraveling mystery would take a fiery turn.

At the very same site where the fire had been attempted, someone succeeded and started a blaze that swept across the reeds on the banks of Prospect Park lake, scorching 30 yards of phragmites — the invasive species that blankets portions of the lake front. Friday morning, all that was left was an ashy wasteland scattered with glass bottles and beer cans. The smell of cinder was still in the air.

“We do have homeless people camp out in the phragmites, but not usually there,” said Eugene Patron, a spokesman for the park. “Sometimes they’ll light a fire — but it’s too damp. It’s weird.”

Anne Wong, the head of landscape management at the park, said that the “phrag” must have burnt out on its own, adding that the culprit could just as easily be rowdy kids causing trouble. Patron said the police had not been alerted during any of the sinister nocturnal activities.

Many questions remain unanswered. Who — or what — left all the blood on the rocks (which the rain has since rinsed clean)? Did some malicious madman smash the turtles that bask in the sun near the boathouse? Lastly, who started the fire, and was it an ill-fated attempt to cook some illicit avian or reptilian meat?

Or is something else entirely going on?

Prospect Park officials are investigating, but have nothing so far.

“We don’t know whether there is a connection or just an unfortunate coincidence,” Patron said. “It’s all these weird pieces, but nothing concrete.”